Add QC to ensure that if we provide evidence for a subset, the mapping must be exact

[matentzn]

This QC check was created as a follow up to #7681

It ensures that, if a subset is declared for a term in ORDO the evidence for it (and ORDO code) must correspond to an exact mapping as well. So:

If

MONDO:123 subset: ordo_disease {source="Orphanet:123"} 

There must also be an exact mapping to Orphanet:123.

[twhetzel]

@matentzn I have not reviewed this since it the QC failed

[matentzn]

I assigned this to you because the QC needs to be fixed by a curator! It fails because of the test..